Centrifugal atomizing device

ABSTRACT

In a centrifugal atomizer comprising a rotatable disc, a plurality of pins mounted normally on the perimeter of the disc, and an upper annular plate mounted on the pins and parallel to the disc, erosion of the disc and annular plate is reduced by outwardly flaring the ends of the pins.

United States Patent 1 Miller 51 Jan. 16,1973

l l l 1 1 CENTRIFUGAL ATOMIZING DEVICE Ralph N. Miller, Newark, Del.

Assignee: E. l. du Pont de Nemours and Company, Wilmington, Del.

Filed: March 15, 1971 Appl. No.1 124,497 I Related U.S. Application Data Continuation-impart of Ser. No. 849,440, Aug. 12, 1969, abandoned.

lnventor:

U.S. Cl ..239/222.l 1, 239/380 Int. Cl. ..B05b l/26 Field of Search ..239/214, 222.11, 222, 223,

Primary Examiner-M. Henson Wood, .lr. Assistant Examiner-Michael Y. Mar Attorney-Donald A. Hoes [57] ABSTRACT In a centrifugal atomizer comprising a rotatable disc, a

plurality of pins mounted normally on the perimeter of the disc, and an upper annular plate mounted on the pins and parallel to the disc, erosion of the disc and annular plate is reduced by outwardly flaring the ends of the pins.

' 2 Claims, 3 Drawing Figures a" mun PATENTEDJAM 18 I975 3.711.025

SHEET 2 [IF 2 INVENTOR Q 3 BY w Mm ATTORNEY CENTRIFUGAL ATOMIZING DEVICE CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 849,440, filed Aug. l2, 1969 now abandoned.

BACKGROUND OF THE INVENTION This invention pertains to an improved design for a centrifugal atomizer of the general type in which there is a rotating disc, a plurality of pins mounted normally on the perimeter of the disc, and an upper annular plate mounted on the pins and parallel to the disc. Such an atomizer serves, e.g. in a spray drier, to disperse fluids or slurries of pulverulent solidsthrough the effect of centrifugal force.

A centrifugal atomizer of the above mentioned type is subject to troublesome wear on the pins, disc, and upper plate even when used with only slightly abrasive materials. Cylindrical pins, as heretofore used, have formed right angle junctures with the disc and with the plate, the result being that a concentration of abrasive wear quickly occurs at the junctures, i.e. giving rise to deep grooves in the regions of the disc and plate adjacent the pin. Whereas abrasive wear on the pins themselves can be minimized by constructing the pins from hard materials such as metal carbides, cermets and ceramics, these same materials are unsuitable for construction of the disc and plate because they lack the structural strength of metals and hence cannot adequately resist the high centrifugal force developed by rotation of the atomizer. Attempts to use a hard surfacing treatment for those regions of disc and plate which are most susceptible to wear will reduce but not suitably eliminate the problem of abrasive wear.

SUMMARY OF THE INVENTION In accordance with the present invention the aforementioned problems of abrasive wear of a centrifugal atomizer can be virtually eliminated by the use of pins which are flared outwardly at both ends forming a working surface that is smoothly curved. The flared ends of the pin thus extend to the plane of the disc and to the plane of the upper annular plate, respectively. Preferably, a tangential juncture will occur where the pin joins the disc and annular plate.

FIG. 1 depicts an axial cross-sectional view of a pin used in accordance with this invention.

FIG. 2 shows a centrifugal atomizer adapted for use in a spray drier, with a vertical cross-sectional view of the interior displayed in a cutout.

FIG. 3 is a cross section normal to the axis along radius 33 of FIG. 2.

In the drawings, improved pin is perpendicularly located between a disc 20 and annular upper plate 16. The disc and annular upper plate each have an inner plane which faces the other. The pin is constructed with flared sections 12 which tangentially approach the inner plane of the disc and the inner plane of the annular upper plate in such a manner that the surfaces of the disc, pin and annular upper plate join in a smooth curve. The pin is provided with a cylindrical projection 14 at the disc end which is then recessed into the disc for stability against centrifugal force. The annular upper plate is rovided with Ii 34 which provides a recess in WhlC the pin fits t ereby increasing the strength of the pin to withstand centrifugal force. A bolt 18 passes through the annular upper plate, pin and disc in order that they remain in their desired position. In order to securely join the disc to an axially located rotating drive means 24, hub section 22 is integrally attached to disc 20 adjacent to the rotating drive means. As shown in FIG. 3, the flares of the pins vconterminously fit with the adjacent pins as sectors of an annular ring thus completely covering the peripheral area 28 of the disc. Feed inlet pipe'30 is positioned between the annular upper plate and hub section perpendicular to the plane of the disc. The atomizer is surrounding by concentric chamber 32. The atomized material leaves the chamber through outlet hopper 36.

The improved pin of this invention has a working surface that is smoothly curved in order to substantially reduce the concentration of abrasive action which would occur at a sharp juncture. Preferably the smoothly curved pin is constructed so that the flare has at least a minimum radius of curvature of one-eighth inch to prevent serious erosion of the plate, disc and the pin. Sharper curvatures tend to concentrate wear in much the same manner as the prior non-flared pins. It is preferable to have the surface of the flared section approach the plane of the disc and the plane of the plate tangentially so as to further reduce the abrading action of the material being dispersed. Additional protection of the disc and plate is provided by designing the flared sections to conterminously fit with the flared sections of the adjacent pins thereby completely covering the peripheral area of the disc and of the plate. Bolts passing through the plate and disc and through a vertical axis of the pin secure the assembly.

In operation, the material to be treated, for example, a slurry of pigmentary titanium dioxide particles, is fed between the annular upper plate and the hub. The spinning of the disc forces the slurry violently outward by centrifugal action causing atomization of the slurry. The curvature on the pins effectively prevents abrasive wear of the pins and, more importantly, adjacent regions of the disc and plate. The atomized slurry can then be contacted with air or another vapor to effect drying.

What is claimed is:

1. In a centrifugal atomizer comprising a disc, an axially located drive means for rotating the disc, a plurality of pins mounted normally to the disc on the periphery thereof, and an annular plate mounted on the pins and parallel to the disc; the improvement wherein the ends of the pins are outwardly flared to provide smoothly curved junctures with the disc and with the plate, said junctures having a minimum radius of curvature of one-eight inch.

2. A centrifugal atomizer according to claim 1 wherein the outwardly flared portions of the pin tangentially approach the disc andplate, respectively. 

1. In a centrifugal atomizer comprising a disc, an axially located drive means for rotating the disc, a plurality of pins mounted normally to the disc on the periphery thereof, and an annular plate mounted on the pins and parallel to the disc; the improvement wherein the ends of the pins are outwardly flared to provide smoothly curved junctures with the disc and with the plate, said junctures having a minimum radius of curvature of one-eight inch.
 2. A centrifugal atomizer according to claim 1 wherein the outwardly flared portions of the pin tangentially approach the disc and plate, respectively. 